Moreover, an RIS, as a large passive scattering array, generally has remarkable capabilities to sense the environments, which has motivated research activities towards the integration of sensing and communications (ISAC) in RIS aided systems. The main objective of an ISAC system is to enable coexistence between the communication and sensing functionalities by ensuring reliable communications with the users while using the same spectrum for sensing and localizing targets [1]}, [2]}, [3]}. The authors of [4]} employed one RIS for both sensing and communication where the direct path between the dual function radar and communication BS and the target exists. The goal was to maximize the radar signal-to-interference-plus-noise ratio (SINR) under the communication SINR constraint. The authors of [5]} proposed an RIS that is adaptively partitioned into two parts for communication and localization, respectively, when no direct path exists.
